Today, the leading contender for the next pandemic of influenza is H5N1, a strain of avian virus. Prevention and control will depend on the rapid production and worldwide distribution of specific pandemic vaccines. Candidate 'pandemic-like' vaccines must be developed and tested in clinical trials to determine the most optimal formulation and the best vaccination schedule. This study is designed to test in healthy adults aged above 18 years the reactogenicity and immunogenicity of one and two administrations of a candidate pandemic H5N1 vaccine formulated from Split Virus.